CVE-2026-7192: Dbit T-CPE301K Buffer Overflow DoS Vulnerability

CVE-2026-7192 Overview

CVE-2026-7192 is a stack-based buffer overflow vulnerability affecting the Shenzhen Dbit T-CPE301K 4G WiFi minirouter. An authenticated attacker can send a manipulated HTTP POST request to the /js/common/do_cmd.js endpoint containing an excessively long parameter. The oversized input overwrites the program counter (PC) and return address (RA) registers, causing a denial of service (DoS) and a full system reboot.

The flaw is classified under CWE-121: Stack-based Buffer Overflow. It is network-exploitable with low attack complexity but requires prior authentication to the router's web management interface.

Critical Impact
Authenticated attackers can crash the router on demand and potentially achieve control-flow hijack through PC/RA register corruption.

Affected Products

Shenzhen Dbit T-CPE301K 4G WiFi Minirouter
Firmware exposing the /js/common/do_cmd.js endpoint
Deployments accessible over the network without additional access controls

Discovery Timeline

2026-09-29 - CVE-2026-7192 published to the National Vulnerability Database (NVD)
2026-09-29 - Last updated in NVD database

Technical Details for CVE-2026-7192

Vulnerability Analysis

The vulnerability resides in the HTTP request handler serving the /js/common/do_cmd.js endpoint. The handler copies parameter data from an incoming POST request into a fixed-size stack buffer without validating the input length. When an authenticated attacker submits a parameter exceeding the buffer boundary, adjacent stack memory is overwritten.

The overwritten memory includes the saved program counter (PC) and return address (RA) registers used by the MIPS or ARM-based processor typical of embedded routers. Corruption of these registers redirects execution to an invalid address, triggering an exception and forcing the device to reboot.

Because the PC and RA registers are directly controllable through the overflow, the vulnerability may extend beyond denial of service. An attacker with knowledge of the firmware layout could potentially craft input that redirects execution to attacker-controlled instructions, escalating impact to arbitrary code execution on the router.

Root Cause

The root cause is missing bounds checking in the parameter-parsing routine of the router's web management interface. The handler trusts the length of user-supplied POST data and performs an unsafe copy operation into a fixed-size local buffer, matching the classic [CWE-121] pattern.

Attack Vector

Exploitation requires network access to the router's HTTP management interface and valid authentication credentials. The attacker issues a crafted POST request to /js/common/do_cmd.js with an oversized parameter value. Processing of the request corrupts stack memory and forces the router into a crash-reboot cycle, disconnecting all downstream clients.

Technical details are documented in the INCIBE Security Notice on T-CPE301K vulnerabilities.

Detection Methods for CVE-2026-7192

Indicators of Compromise

Unexpected reboots of the T-CPE301K router coinciding with HTTP POST activity to /js/common/do_cmd.js
Web server access logs containing POST requests with abnormally long parameter values targeting the vulnerable endpoint
Loss of connectivity for downstream clients followed by router availability gaps in monitoring systems
Authentication events from unfamiliar source addresses immediately preceding router crashes

Detection Strategies

Inspect HTTP request logs on upstream network devices for POST requests to /js/common/do_cmd.js with parameter lengths exceeding typical values
Deploy network intrusion detection signatures that flag oversized POST bodies directed at the router management interface
Correlate router reboot events with preceding authenticated web sessions to identify potential exploitation attempts

Monitoring Recommendations

Enable syslog forwarding from the router to a central log collector to capture crash and reboot events
Monitor administrative authentication attempts against the router's web interface for brute-force or credential-stuffing activity
Alert on repeated device unavailability patterns that may indicate active denial-of-service exploitation

How to Mitigate CVE-2026-7192

Immediate Actions Required

Restrict access to the router's HTTP management interface to trusted management VLANs or specific administrator IP addresses
Rotate all administrative credentials on affected T-CPE301K devices and enforce strong, unique passwords
Disable remote WAN-side management if enabled, limiting the attack surface to the local network
Monitor vendor communications from Shenzhen Dbit for firmware updates addressing the vulnerability

Patch Information

No vendor patch has been publicly listed in the NVD entry at the time of publication. Administrators should consult the INCIBE advisory for updates on remediation availability from Shenzhen Dbit.

Workarounds

Place the router behind an upstream firewall that filters HTTP POST requests to /js/common/do_cmd.js exceeding a safe size threshold
Segment the router management interface onto an isolated network unreachable from user or guest subnets
Consider replacing the affected device in high-availability environments where reboot-based DoS is unacceptable until a firmware fix is available

bash

# Example iptables rule limiting access to router management interface
iptables -A FORWARD -p tcp --dport 80 -d <router_ip> -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp --dport 80 -d <router_ip> -j DROP